The present invention relates to an image-forming apparatus, and more particularly, to an image-forming apparatus provided with an exhaust duct.
In an image-forming apparatus employing an electrophotographic recording system, an electrostatic latent image is formed through exposure on the surface of an image carrier formed from a photosensitive element. In this image-forming apparatus, the toner image formed on the surface of the image carrier, the toner image being transferred after the electrostatic latent image has been developed by use of toner, is transferred to a recording medium, such as recording paper, thereby forming an image. The electrostatic latent image can be subjected to toner development, by rotating a development roller opposing the surface of the image carrier and transferring the electrostatic latent image to an outer peripheral surface of the development roller in an adhering manner.
This image-forming apparatus adopting the electrophotographic recording system is provided with a development cartridge which houses toner in a container, along with the development roller opposing the image carrier. Some image-forming apparatus have a rotary development device capable of housing a plurality of development cartridges. In this image-forming apparatus, the rotary development device is rotated around a rotary shaft, thereby switching the development cartridge to be located at a development position where the development cartridge opposes the image carrier.
In such an image-forming apparatus, development cartridges for housing yellow (Y) toner, magenta (M) toner, cyan (C) toner, and black (K) toner are configured as development cartridges for causing toner to adhere to the surface of the image carrier, so that a rotary development device can store (carry) the development cartridges. The development cartridges are sequentially switched, thereby forming a color image on which colors of toner are superimposed. A monochrome image made of one color of toner, for instance, a black-and-white monochrome image made of black (K) toner (hereinafter also called simply a “monochrome image”), can also be formed.
In such an image-forming apparatus, development is performed by use of toner while the image carrier and the development roller are being rotated. For this reason, difficulty is encountered in transferring all particles of the toner on the outer peripheral surface of the development roller to the image carrier or recovering all particles of the toner into the development cartridge. Since the toner is in the form of fine particles, the toner often splashes and floats around a development position where the development roller opposes the image carrier, to thus accumulate or stain recording paper or the like. Therefore, there is proposed an image-forming apparatus adopting an electrophotographic recording system having an exhaust duct for sucking air in the vicinity of the development position and exhausting the sucked air (see, e.g., JP-A-2003-295714).
Recently, silencing of OA equipment has been sought. The image-forming apparatus having such a rotary development device forms an image while continually rotating the rotary development device at the time of formation of a color image. Therefore, noise stemming from driving of the rotary development device, particularly, leakage of noise from a side surface close to a position where the rotary development device is situated, raises a problem.
Moreover, in the image-forming apparatus having such a rotary development device, the toner housed in the development cartridge is greatly influenced by an environment. For instance, when an ambient temperature becomes high, a problem may arise in the quality of the toner.
In contrast, miniaturization of such office automation equipment has recently been particularly sought. Since an internal storage space of the equipment also becomes smaller, difficulty is encountered in avoiding a layout where a rotary development device housing the development cartridges becomes close to heat-producing elements.
Furthermore, as shown in FIG. 15, in the image-forming apparatus having such an exhaust duct, an exhaust duct 130 has an inlet 131 located at a position above the neighborhood of a development position where a development roller 14c of the rotary development device 14 opposes a photosensitive drum 12, and is provided such that a path extending from the inlet 131 to a position above the rotary development device 14 is taken as an exhaust path 132. Since an intermediate transfer belt 15 is provided at a position above the rotary development device 14, the exhaust duct 130 is also provided at a position adjacent to an intermediate transfer unit 25 which actuates the intermediate transfer belt 15.
A pair of duct plates 141a, 141b formed along an exterior surface of the rotary development device 14 oppose each other to thus form an exhaust passage of an exhaust path 132 in this exhaust duct 130. A filter 134 for adsorbing toner absorbed in sucked air is provided at any position in this exhaust path 132.
However, in such a related image-forming apparatus, the duct plate 141a of the exhaust duct 130 is provided separately from a unit cover 25a of the intermediate transfer unit 25. As shown in FIG. 16, there is adopted a structure where, when the intermediate transfer unit 25 is removed for performing maintenance of the intermediate transfer belt 15, the unit cover 25a is removed.
Specifically, since the exhaust duct 130 is not designed to be removed from the main body of the apparatus, the exhaust path defined between the duct plates 141a, 141b cannot be opened during the period of ordinary maintenance. Even when the sucked toner has been accumulated in the exhaust path, the toner cannot be cleaned. Therefore, on some occasions, when the image-forming apparatus has been subjected to shock during, e.g., movement, there may be a risk of the accumulated toner contaminating the inside of the apparatus.
Although FIGS. 15 and 16 show the intermediate transfer unit 25 having the unit cover 25a, the intermediate transfer unit is not limited to this type. An intermediate transfer unit not having the unit cover 25a suffers the same problem, as well. The rotary development device 14 can be removably attached while being withdrawn along the direction of a rotary shaft of the rotary development device, without regard to the exhaust duct 130.